Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Title: [Sleeping channel measurements for body area networks] Date Submitted: [November, 2009] Source: [Dino Miniutti 12, David Smith 12, Leif Hanlen 12, Andrew Zhang 12, Athanassios Boulis 1, David Rodda 1, Ben Gilbert 1 ] Company [NICTA 1, The Australian National University 2 ] Address [7 London Circuit, Canberra, ACT, 2600, Australia] Voice:[+61-2-6267-6256], FAX: [+61-2-6267-6220], E-Mail:[dino.miniutti@nicta.com.au] Abstract: [300+ hours of sleeping BAN channel measurements with characterisation of data in terms of outages with respect to receiver sensitivity. Showing that channel outages are greater than 10% with -100 dbm receiver sensitivity.] Purpose: [To help design and evaluate BAN systems.] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Slide 1
Sleeping channel measurements for BAN NICTA & The Australian National University Dino Miniutti, David Smith, Leif Hanlen, Andrew Zhang NICTA Athanassios Boulis, David Rodda, Ben Gilbert Slide 2
Outline Motivation: People have asked about what happens to the BAN channel when people are sleeping Have done some sleeping measurements People at home in bed (not hospital) Analysis: Channel gain distribution Outage probability Outage duration Outage = Received power < Receiver sensitivity Slide 3
Experiment setup Using NICTA s body-worn channel sounder (same one used in previous measurements) Measured people sleeping/lying in bed Majority of data is for people sleeping 12 subject measurements (8 different adults) Each measurement 2 hours or more (over 300 hours in total) Just outside 2.4 GHz ISM band (to avoid ISM interference) 0 dbm transmit power RSSI sampled every 15 ms 183 link measurements 85 on-body to on-body 98 on-body to off-body Slide 4
Measurement positions Device positions Next to bed (head) Left wrist Hip (front) Next to bed (foot) Right wrist Hip (back) Left ankle Device type Tx/Rx Tx/Rx Tx/Rx Rx Rx Rx Rx Slide 5 Transmitting devices also receive packets from all other transmitters. Physically they are the same, but they run different firmware
Typical measurement (example) General trend is for long periods where RSSI is stable Gaps in figure correspond to RSSI dropping below channel sounder receive sensitivity (approx: -100 dbm) Including all data, this occurs 14.8% of the time for on-body and 14.9% of the time for off-body channels Slide 6
Channel gain distribution Lognormal distribution is best fit Median channel attenuation: On-body: 79.5 db Off-body: 81.5 db Generally larger attenuation than non-sleeping channels Slide 7
Outage probability Best case outage probability (attenuation > 100 db) is more than 10% for both on-body (13.5%) and offbody (10.9%) channels Slide 8
Outage duration (on-body to on-body only) Showing percentage of time that continuous outages of larger than x seconds (on horizontal axis) occur in all on-body to onbody measurements Example: A receiver with a sensitivity of -88 dbm will experience outages of larger than 1000 seconds 5% of the time Long (duration) outages are infrequent, but because they are long, they take up a large fraction of the total time Slide 9
Comments On-body and off-body results are very similar. Attenuation effects are from the same sources Shadowing from body Antenna orientation Distances are similar (substantially less than 3m) This sort of attenuation is not frequency dependent can not change channel within same band to avoid More attenuation than non-sleeping channels Minimum PER > 10% with -100dBm receive sensitivity Long outages are infrequent, but they account for a large percentage of the total time Slide 10